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Sept, 6, 1932 R.- R. DU PUY 1,315,429

I LOUD SPEAKER MODULATING MECHANISM Filed Aug. 10, 1931 2 Sheets-Sheet 1 I mamammxm Sept. 6, 1932. R R DU PUY 1,875,429

LOUD SPEAKER MODULATING MECHANISM Filed Aug. 10, 1931 Sheets-Sheet 2 IN VENTOR flat/102 82 3. flu Pa ATTORNEY Patented Sept. 1932 I UNITED STATES PATENT orrlca RICHARD B. DU PUY, 8'1. PAUL, MINNESOTA, ASSIG ITOB TO WRIGHT-DE OOSTEB, mo,

01 ST. PAUL, MINNESOTA, A CORIOBATION OF MINNESOTA a Loon-arm nonumrme uncnmm Application and augm 10, m1. mi Io. 550,044.

The present invention relates to a loud speaker modulating mechanism. 7

In the reproduction of sound waves where the sound waves are either recorded in a groove in a record of the phonograph type, or where the sound waves are photogra ihed on a film, as is practiced in the making 0 certain types of sound moving pictures, it has been found that in either of the above mentioned methods of sound reproduction that in recording sound im ressions, either upon a record or film, that t to low notes are accentuated and the high notes are slightly attenuated. I

An object of the present invention is to make an electrical sound reproducing mechanism by which sound tones of difierent wave lengths and frequencies may be modified with respect to other tones of ditl'erent sound frego queucies reproduced by said mechanism.

In order to attain this object, there is provided. in accordance with one. feature of the invention, a sound reproducing'mechanism having a vibratory diaphragm and electro. magnetic means to cause a vibration of said diaphragm to produce sound waves, said diaphragm being enclosed on one face thereof by a housing having adjustable openings therein.

These and other features of the invention will be more fully brought out in the following description and the accompanying drawings, wherein:

Figure 1 is a view in side elevation of an electrical loud speaking mechanism having the present invention embodied therein.

Figure 2 is a rear view of the mechanism shown in Figure 1.

Figure 3 is a sectional view in reduced scale showing housing members mounted therein. said housing members having openings therein which may be moved relatively with respect to each other so as to have the openings of the inner and outer housing members register with each other in one position, and to havesaid openings moved out of reg istry with each other in another position to form a substantially unperforated housing in rear of a vibratory diaphragm: and

Figure 4 is a view in side elevation of a loud speaker embodying the present invention a portion of the housing and a portion i of the cone dia hragm being broken aim to more clearly disclose the structure thereo Referring to the drawings in detail, aloud speaker mechanism which is of a well known type with the exception of the cone supportin housing, comprises a supporting stand 1, a ield coil housing member 2, and a cone 3. The interior construction of the loud speaker may be of any suitable type; In fact, even the particular shape of the diaphragm is not material to the invention, so that it is not intended to restrict the invention to any particular form of sound reproducing mechanism, other than that such mechanism shall have a vibratory diaphragm adapted to produce soundwaves of varying frequencies and wave lengths.

Inthe present construction a cone-shaped sheet metal housing member 4 is provided with a plurality of openings 5 therein and is provided with a marginal, flange 6 on its outer or larger end to grip the edge of a vibratory cone '3. An inner cone-shaped. member 7 which terminates short of the flange 6 and which also terminates short of thesmaller I or inner end of the cone-shaped housing member 4 is provided with openings 8 which are adapted to register with the openings 5 in the outer housing member 4, The inner housing member 7 is provided with knobs 9 which lie in Slot-ted openings 10 in the outer housing member 4. One of these knobs 11 is screw threaded so thatv the inner housing member 7 may be secured in an adjusted position with respect to' the outer housing member 4. When the openings in the inner and outer housing members are moved into registry, with each other, the area between the vibratory cone'3and thehousing members 4 and 7 will be in open communication with the exterior atmosphere so that no restrictive or damping action is performed by the structure and the mechanism is in all respects similar in operation to the ordinary type of loud speaker at present on the market in which vents are provided in the housing member similar to the openings 5 in the outer casing 4. When, however. the inner housing member 7 is rotated with respect to the outer housing member 4 so as to bring the o enings in the inner and outer housing memhers out of registry with each other, this closes the openings in the outer housing member 4 and provides a 5 substantially solid Wall spaced rearwardly a short distance from the cone 3. Vith the openings 5 closed in this manner the larger Vibrations of the cone 3 caused by the deeper notes and longer sound wave and lower frequency set up a pulsation in this restricted area which tends to dampen or attenuate said lower notes. The higher sound frequencies are not noticeably affected by this restriction and the result is that the higher notes are reproduced in their full recorded strength, that is, with the same strength that they would be if no such restricting means were present. The lower notes are, however, modulated so that the error present in the recorded sound, as above set forth, may be cor rected by adjusting the size of the openings in the housing member.

I claim: 1. In an electrical sound reproducing g5 mechanism, a vibrator diaphragm, means operatively connected to said diaphragm to cause a vibration thereof to produce sound tones of varying frequencies, and an enclosure being positioned in slightly spaced position from over one side of said diaphragm, said enclosure having variable oienings therein to modulate tones of lower requencies produced by vibration of said diaphragm.

2. In a sound reproducing mechanism, a rihratory member, means operatively connected to said vibratory member to cause a vibration thereof to produce sound tones, a restricted enclosure positioned in slightly spaced relation from said diaphragm over one side thereof. and a variable opening in said enclosure to vary the restrictive action of said enclosure. on the vibrations of said diaphragm.

3. In an electrical sound reproducing mechanism, a vibratory diaphragm, means operatively connected to said diaphragm. to

cause a vibration thereof to produce sound tones of varying frequencies, and an enclosure over the rear of said diaphragm spaced 5U slightlytherefrom to cause a damping action of tone vibrations of low frequencies, said enclosure having variable openings therein to reduce said damping action.

In testimony where f I aflix my signature RICHARD R. DU PUY. 

